Source: https://code.google.com/p/google-security-research/issues/detail?id=509
The attached testcase crashes Window 7 32-bit with Special Pool enabled on win32k.sys due to a use-after-free condition. The bug appears to be a race condition between two threads and multiple runs on the PoC might be required to trigger the bug. This is more reliable on systems with multiple cores.
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Proof of Concept:
https://github.com/offensive-security/exploit-database-bin-sploits/raw/master/bin-sploits/38795.zip